1. Field of the Invention
The present invention relates to a device for detecting objects in a closed container and its use in providing an "electronic mailbox" which allows remote detection of mail present in the box.
2. Discussion of the Background
In many parts of the United States, especially rural areas, mailboxes are remotely located with respect to the residence of the person to whom the mailbox belongs. Often this distance can be as much as several hundred yards or more, making it necessary to travel outside, often in inclement weather, in order to determine if mail is present.
Previous attempts to provide a device which indicates the presence of mail in the mailbox have been primarily mechanical devices, ranging from flags that pop up when the door of the mailbox is open, to springs with small ribbons on them. These previous attempts rely on the opening of the door of the mailbox as a signal that mail has been placed in the box. However, such an approach does not work if the door has been inadvertently opened and closed, if the springs or flags have not been reset or at night.
Benages, U.S. Pat. No. 4,794,377, discloses one solution which has been proposed. In Benages, a device is disclosed which is attached to the mailbox and detects the presence of mail by using an optical sensor which requires either a radio-frequency transmitter and receiver to indicate the presence of mail in the mailbox or requires that the mailbox be directly wired to the electrical wiring of the residence. The optical sensor uses a photodiode attached to the top of the mailbox which receives a signal from an infrared emitter located on the bottom of the mailbox. The presence of mail in the box interrupts the signal from the emitter to the photodiode and triggers the radio transmitter to notify the receiver.
However, since many rural areas have high voltage power lines which generate electrical fields, many remote mailboxes are located adjacent to highways with heavy traffic among which are numerous cellular phones and radios, and countless other sources of potential radio frequency interference, the signal from the device of Benages can be disturbed to provide false negative or false positive signals. Additionally, the device of Benages requires modification of the mailbox and correct alignment of the components of the optical sensor. If security is a concern, the device of Benages suffers from the disadvantage that radio frequency scanners can intercept the signal produced.
Accordingly a device is needed which can detect and signal the presence of objects, such as mail, in a remotely located container, such as a mailbox, which does not suffer from the above-noted disadvantages, which is easy to install and has very low power consumption.